In complex mechanical systems, the study of power consumption and performance, the design of their structure as well as the study of the lubrication state between the various module groups and the measurement of important parameters such as the friction between the various components have been of great importance for many years. Due to the complex movements within machinery, the harsh environment and the relatively small friction forces, which make measurement very difficult, it is particularly important that these data are measured accurately.

　　The use of wireless transceivers, using sensor signals to transmit signals via wireless transceiver circuits, allows data to be stored and then read from the memory card into the computer for analysis, providing a new method of data acquisition for complex systems with precise data requirements. In addition, at high acquisition frequencies, the volume of data is relatively large, which places high demands on the processor processing speed, RF radio transmission speed, interface transmission speed, A/D conversion speed and power consumption of the acquisition system, as well as the internal size of the mechanical system, making it difficult. This makes the design of the data acquisition circuit board the key to the data acquisition system, and we need to design special data acquisition and wireless transceiver devices.

　　Measurement system principle

　　The system consists of a sensor, power supply, signal conditioning circuit, signal processing circuit and a PC. In practice, the sensor is mounted on a moving part, and as the use of leads to transmit signals can restrict the movement of mechanical parts, wireless transceiver circuits can be used to transmit the data. computer.

      The signal processing circuit can be used to convert the analogue signal into a digital signal and then store it on the memory card. The signal conditioning circuit of the thermocouple outputs a 12-bit SPI format digital signal, which can be stored directly on the memory card by the microcontroller. The capacity of the memory card should ensure that the acquisition time is sufficient (for an acquisition frequency of 3000 Hz, a memory card of more than 512 M can guarantee an acquisition time of at least 25 minutes). The design of the DC bridge circuit is a key part of the measurement system and will be analysed in detail in the following section.

　　The strain gauge DC bridge circuit

　　The strain gauge conditioning circuit consists of a booster chip (which provides the working voltage for the chip), a voltage reference (voltage regulator), a bridge, a filter and an amplifier.

      The strain gauge model 350-2AA was selected for the measurement circuit, with a strain sensitivity factor of K=2.18 (a dimensionless positive number), a nominal resistance of 350Ω and a wire grid size of 2 x 2mm; the DC single-arm bridge was used to achieve the resistance-to-voltage conversion, taking into account the small space available on the connecting rod and the need to install as few sensors as possible. The design of the DC bridge measurement circuit of the resistance strain gauge in the wireless transceiver data acquisition system has been completed. Of course, when we design the data acquisition system, according to the actual measurement needs, such as the system operating environment is affected by temperature, frequency and some other environment, the measurement parameters are different, resulting in the data acquisition system is not exactly the same, the designer can modify according to the needs. This paper focuses on the design of a strain gauge DC bridge for wireless data acquisition systems, and proposes a viable solution for complex mechanical control systems where data acquisition is difficult.